Ronaldo tested positive for COVID-19 earlier in October while away on international duty, forcing him to miss four matches across all competitions.
Juve only managed to win one of those four games, a 2-0 UEFA Champions League victory over Dynamo Kiev, as it was held to Serie A draws by Crotone and Hellas Verona, before losing 2-0 to Barcelona at home on Thursday (AEDT).
The club confirmed on Saturday (AEDT) that Ronaldo, 35, finally returned a negative test result, meaning he was no longer required to self-isolate, but he was still due to undergo a medical examination before the game.
It seems Ronaldo has since passed such a test, with Pirlo revealing the five-time Ballon d'Or winner is travelling with the squad.
"I found him well, even the second swab was negative, so he is fine and will set off with us," the former Italy international said.
"I don't think he'll play from the beginning – the important thing is to have him available: he is a fundamental player.
"He trained at home, but it's not the same as doing it on the pitch."
Matthijs de Ligt remains a week or so away from a return, however, with the Dutch defender yet to feature this term after having shoulder surgery in August.
"Unfortunately, we will have to wait another week, as the orthopaedist requested of us. Until now, however, everything has gone well, he is training with the team but he still needs a few days," Pirlo said.